1. Field of the Invention
The present invention relates to machine tools, and in particular, to a machine tool that includes a controller for controlling a viewing window.
2. Description of the Related Art
A transparent viewing window that can be seen from outside is provided in many splash guards or opening/closing doors of machine tools. Such viewing windows are used mainly for machining state observation, and operation check in trial processing or trial working. These viewing windows are indispensable for the machine tools to modify a machining program or to complete the machining program.
However, its visibility is decreased when coolant used in an actual cutting operation or swarf flies to gradually adhere to the viewing window. To remove the adhering substances from the viewing window, some methods of blowing air to clean the substances or methods of cleaning the substances with a wiper are provided. However, it is difficult to completely remove the adhering substances caused by the coolant from the viewing window with air or the wiper, and in some cases, it is difficult to look the inside of the machine tool. To solve the problems, Japanese Unexamined Utility Model Registration Application Publication No. 61-184644 discloses a double structure for covering a viewing window with a block plate to prevent the generation of smudges due to adhesion of coolant to the viewing window.
Japanese Unexamined Utility Model Registration Application Publication No. 61-184644 discusses that a block plate may be opened or closed manually, automatically, or by any method (lines 8 to 9 in page 4). However, the publication does not refer to automatic determination of the necessity of blocking the viewing window with the block plate. Accordingly, the operator has to open or close the block plate when the operator determines that it is necessary to block the viewing window with the block plate, and this operation is troublesome for the operator.